These have a radiate arrangement externally, but are of irregular structure at their centres; it is interesting to note that in both rocks melanite is an important accessory.
12.
There are two kinds of composition, one is high alkali, alumina, silicon and barium containing melanite garnet; the other is high in potassium with nepheline and hauyne.
13.
In Finland, melanite bearing nepheline rocks have been found and described as ijolite, but the only other locality for melanite-leucite-syenite is Magnet Cove igneous complex in Arkansas.
14.
In Finland, melanite bearing nepheline rocks have been found and described as ijolite, but the only other locality for melanite-leucite-syenite is Magnet Cove igneous complex in Arkansas.
15.
The brightly glittering black sands of the beaches are made of crystals of melanite garnet, barkevikite hornblende, and magnetite eroded from the uncompahgrite lava fragments in the agglomerates that overlie the fossil beds.
16.
The latter is the rarest and most costly of the garnets, with three of its varieties topazolite ( yellow ), melanite ( black ), and demantoid ( green ) sometimes seen in jewelry.
17.
At the margins of the outcrop patches of nepheline syenite occur; usually the nepheline is decomposed, but occasionally it is well preserved; the other ingredients of the rock are brown garnet ( melanite ) and aegirine.
18.
The presence of the following minerals precludes a rock from being classified as a lamproite : primary plagioclase, melilite, monticellite, kalsilite, nepheline, Na-rich alkali feldspar, sodalite, nosean, hauyne, melanite, schorlomite or kimzeyite.
19.
Sanidine, melanite, hauyne and perovskite are frequent accessory minerals in these rocks, and many of them contain melilite in some quantity, The well-known leucitite of the Capo di Bove, near, Rome, is rich in this mineral, which forms irregular plates, yellow in the hand specimen, enclosing many small rounded crystals of leucite.
